Researchers make solar cell with 40.8 percent efficiency

Scientists at the U.S. Department of Energy's National Renewable Energy Laboratory (NREL) have developed world's first solar cells with an efficiency of 40.8 percent. It's slightly better than the previous record holder but one thing to keep in mind here is that these solar cells are only cost-effective for usage in space applications like satellites. High-efficiency solar cells typically use expensive rare metals and have complicated production processes which make them unsuitable for commercial production.

This is the highest confirmed efficiency of any photovoltaic device to date.

The inverted metamorphic triple-junction solar cell was designed, fabricated and independently measured at NREL. The 40.8 percent efficiency was measured under concentrated light of 326 suns. One sun is about the amount of light that typically hits Earth on a sunny day. The new cell is a natural candidate for the space satellite market and for terrestrial concentrated photovoltaic arrays, which use lenses or mirrors to focus sunlight onto the solar cells.

The new solar cell differs significantly from the previous record holder – also based on a NREL design. Instead of using a germanium wafer as the bottom junction of the device, the new design uses compositions of gallium indium phosphide and gallium indium arsenide to split the solar spectrum into three equal parts that are absorbed by each of the cell's three junctions for higher potential efficiencies. This is accomplished by growing the solar cell on a gallium arsenide wafer, flipping it over, then removing the wafer. The resulting device is extremely thin and light and represents a new class of solar cells with advantages in performance, design, operation and cost.